PINEAL EYE IN LACERTILIA. 233 



(4) There is not sufficient evidence to prove or 

 disprove the existence of the organ within the 

 group Pisces; it was present in extinct Amphibia, 

 and is found amongst living forms only in Lacertilia. 



(5) In all forms at present existing it is in a 

 rudimentary state, and though its structure is 

 better developed in some than in others, it is per- 

 fectly functional in none. 



(6) It was present most highly developed in 



(1) Extinct Amphibia (Labyrinthodonta), and 



(2) The large group of extinct forms (as Ich- 

 thyosaurus, Plesiosaurus, Iguanodon, &c.) which 

 may be regarded as ancestors alike of living 

 Reptilia and Aves. 



(7) The pineal eye may probably be most rightly 

 considered, as peculiarly a sense organ of pre-Ter- 

 tiary periods. 



